A HVAC system commonly utilizes heat exchangers to help exchange heat between refrigerant and another fluid (such as air or water) moving through the heat exchangers. For example, during a cooling cycle, compressed refrigerant vapor is typically directed to a condenser. The condenser may be configured to facilitate heat exchange between the compressed refrigerant and the environment and condense the compressed refrigerant vapor into liquid refrigerant. The liquid refrigerant is then typically directed through an expansion valve to become a refrigerant vapor/liquid refrigerant mixture (two-phase refrigerant). The two-phase refrigerant is then typically directed into an evaporator, where the two-phase refrigerant exchanges heat with air in a room to be cooled. During the heat exchanging process, the two-phase refrigerant usually absorbs heat and is vaporized in the evaporator. The vaporized refrigerant is then directed back to the compressor.
Some HVAC systems are also configured to have a heating cycle. During a heating cycle, the process is usually reversed from the process in the cooling cycle. The evaporator functionally works as a condenser, and the condenser functionally works as an evaporator. After being compressed by the compressor, the compressed refrigerant vapor is typically directed to the evaporator first so as to release heat to the indoor air, which also condenses the refrigerant vapor to liquid refrigerant. The liquid refrigerant is then typically directed to the condenser to absorb heat from the environment and is vaporized. In the heating cycle, a direction of the refrigerant flow is typically reversed from a direction of the refrigerant flow in the cooling cycle.
Various types of heat exchangers have been developed to work as a condenser and/or an evaporator. One type of heat exchanger is a micro-channel heat exchanger (MCHEX). A typical MCHEX may include micro-channel tubes running in parallel between two headers. The adjacent tubes generally have fan-fold fins brazed in between. Refrigerant can be distributed into the micro-channel tubes from one of the headers. Outer surfaces of the micro-channel tubes and the fins may help heat exchange between the refrigerant in the micro-channel tubes and the environment.